A need has arisen for a hand tightenable metal screw threaded closure plug to be used primarily in a metal container specially constructed for the temporary storage of materials, particularly combustible fluids. In order to satisfy this need such plug must be capable of easy hand manipulation to produce effective closing under normal circumstances without the aid of any tool or wrench. Threaded steel closure plugs such as commonly employed on steel shipping containers are designed to be actuated by using a wrench. As such, they do not normally lend themselves to effective direct hand manipulation.